NAD!!!

[dave_mc]

^ yeah I think so. i've only tried the 50 i have, but i think the 20 has less gain. they brought out the 22 more recently which (i think) is the higher gain preamp of the higher wattage heads coupled with the ~20 watt EL84 power section.

[Nadz1lla]

Aye he's not been able to tell me who did it, yet, which makes me a little bit "hmmm...", but I've not even tried the A/Bing, just been using it as a normal amp. The two channels work well, though.

I have a feeling I will be sending this to someone in the future to see about taking out some of the modding and replacing it with something I'll actually use more, maybe. We'll see.

After a bit more playing, I might want to look at other tube options. It's SO close to "my" sound but not quiiiiiiiite there yet. I have an EQ pedal to try in the chain and my noise suppressor with it's unforeseen but rather nice tonal side-effect. I have a lot of playing around and experimenting to do before I go thinking about mods.  :lol:

[Toe-Knee]

Aye he's not been able to tell me who did it, yet, which makes me a little bit "hmmm...", but I've not even tried the A/Bing, just been using it as a normal amp. The two channels work well, though.

I have a feeling I will be sending this to someone in the future to see about taking out some of the modding and replacing it with something I'll actually use more, maybe. We'll see.

After a bit more playing, I might want to look at other tube options. It's SO close to "my" sound but not quiiiiiiiite there yet. I have an EQ pedal to try in the chain and my noise suppressor with it's unforeseen but rather nice tonal side-effect. I have a lot of playing around and experimenting to do before I go thinking about mods.  :lol:

What don't you like about the current mods?

Regarding valves what are in it currently? I imagine a set of tungsol 12ax7s in the preamp will push it closer to suiting your style.

[Nadz1lla]

I don't dislike the mods as such, just that whilst it's nifty, I don't think I'd ever use the A/B mod. Just thinking if something else could go in there and make use of the changes to the chassis etc then it might be worth considering what else is out there. I don't have anything particular in mind at the moment, though.

Not sure what's currently in there in terms of valves, when I get the time I'll open her up and have a good old gander. Working all the hours of the day pretty much this week, heh. Will try to do it at the weekend.  :)

[Dmoney]

post a gut pic. g'waaaaannn!

[Nadz1lla]

So I managed to get some time to take the thing apart for you gut-pic lovers. I haven't got the first clue about which parts you guys find most interesting, so I took close-ups of all of the inside, heh.

Behold!

[Nadz1lla]

...

[Nadz1lla]

...

[Nadz1lla]

Aaaaand last one  :lol:

[Nadz1lla]

THREADOMANCY!!!

Been playing this amp for a while now, and I kind of feel that the high-gain could do with some more grunt. There's a bit too much "fizz" and not enough "guts", if you know what I mean?

Regarding valves what are in it currently? I imagine a set of tungsol 12ax7s in the preamp will push it closer to suiting your style.

I was wondering how I would go about learning which valves create certain sounds, actually. I had a look on t'interwebs for those Tungsol, and they were quite cheap compared to a lot of other valves that were on offer in the same section. What options do you reckon I have in this department, and are valves easy to take out and re-install?
 :)

[Toe-Knee]

THREADOMANCY!!!

Been playing this amp for a while now, and I kind of feel that the high-gain could do with some more grunt. There's a bit too much "fizz" and not enough "guts", if you know what I mean?

Regarding valves what are in it currently? I imagine a set of tungsol 12ax7s in the preamp will push it closer to suiting your style.

I was wondering how I would go about learning which valves create certain sounds, actually. I had a look on t'interwebs for those Tungsol, and they were quite cheap compared to a lot of other valves that were on offer in the same section. What options do you reckon I have in this department, and are valves easy to take out and re-install?
 :)

The preamp valves you can just pull out and swap. The power amp valves will need rebiasing.

I am quite fond of tungsol RI in v1 then JJ ECC83s in the other spots.

Im not sure what to recommend for the power amp as i dont have much experience with el84/6v6 (not sure whats in the jca20)

the JJs will definitely give you more 'guts' the tungsols are pretty high gain and can be bright which is why i only use them in v1.

If you dont like fizz avoid Electro harmonix 12ax7 like the plague. Theyre really bright and aggressive in the high end. They can be great in the right amp though

[dave_mc]

you could also try a tubescreamer-style od pedal, or try different speakers (i like eminence v12s with my 50 watt jet city).

I'm guessing JJs would help on the valve front, but that's only from my experience with them in other amps.

[Nadz1lla]

Cheers guys! Very helpful.

Toe-Knee - thanks I'll have a gander at getting some of those. As for re-biasing, I'm guessing I'd have to drop it into an amp specialist to get that done? I'm handy with building and fixing stuff, but I am guessing "re-biasing" is a little more specialist than taking one thing out and putting another thing in? Also V1 = Clean and V2 = Crunch?

Dave - I am currently using a Bad Monkey, which I had researched a lot prior to buying. It seemed to come really close in most of the video comparisons I watched, and actually preferred the tone it gave over the "real" TS in one of the Tone King's vids. I do like what it adds to my tone, just the right amount of tweaking on the pedal side of things I think, heh.

[Toe-Knee]

To be honest if you do your research regarding your particular amp model and read some safety information biasing an amp is quicker and easier than changing strings on a guitar.

[BigB]

As for re-biasing, I'm guessing I'd have to drop it into an amp specialist to get that done?

Depends on the amp and your own technical skills (and tooling). Some amps don't need biasing at all since the circuit takes care of it ("cathode-biased" aka "self-biased" amps like the Vox AC30 or Tweed Deluxe), some amps have a "bias point" (where you can get a reading of the bias voltage) and a trim-pot to adjust it so all you need is a multimeter, a screwdriver and a few advises from someone more knowledgeable, and finally a lot of amps don't have a bias point or trim-pot in which case, well, getting your amp to a real amp tech might indeed be the simplest (and safest) solution  :lol:

wrt/ your own amp it seems that it has a trim-pot but no bias point so if you have a good multimeter (one that can takes 400+VDC) and feel confortable working with lethal DC voltages here's a starter:

http://www.youtube.com/watch?v=V4T83PgEIhc

Also V1 = Clean and V2 = Crunch?

Here again it depends on the amp. In your case V1 is used for the first two gain stages (12Awhatever7 are double triodes - 2 gain stages in one bottle) so it's a very important part of your tone (everything else will reamplify what comes out of it) and it needs to be a very silent (no hum, no microphonics) tube.  V2 add some more gain and builds the preamp's distortion on what was provided by V1. Now it's not a channel switcher amp and both V1 and V2 are always on , so you can't really think in terms of "V1 clean / V2 crunch" (and FWIW even for simple channel switchers like the HRDx, Classic30 etc, V1 is still always on, you just have the option to switch V2 in and out of the circuit).

(disclaimer: overly simplified answer - I failed to find a decent schematic for the JCA20 and I'm not an amp tech).

[edit]
Rereading your very first post I see yours has been modded for a "clean / crunch " operation. I can't tell for sure what the exact mod is but I suspect it mostly switches V2 out of the circuit like for most regular channel switchers (cf above), so you would have clean -> V1 only, crunch -> V1+V2.
[/edit]

To be honest if you do your research regarding your particular amp model and read some safety information biasing an amp is quicker and easier than changing strings on a guitar.

Well, at least there's no lethal DC voltage involved in changing strings  :lol: